How does the main image at a href="http://www.mcafee.com/us/" rel="nofollow"http://www.mcafee.com/us//a get centered in tableless CSS?

I'm trying to learn tableless layouts using CSS and am having trouble trying to make a

centered (I assume the graphic on the Mcafee website is in a div). So even if you zoom out, you'll still see the image centered. I've tried "text-align: center" but it's still not working.